Frictionless track and gliders having air bearing surfaces for demonstrating mechanical principles



Jan. 24, 1967 J. L. STULL ET AL 3,299,535

FRICTIONLESS TRACK AND GLIDERS HAVING AIR BEARING SURFACES FOR DEMONSTRATING -MECHANICAL PRINCIPLES 2 Sheets-Sheet 1 Filed Nov. L0, 1964 mr N.

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W 7 101- 2, wad- 3L ATTORNEYS Jan. 24, 1 967 I J. STUL ET AL 3,299,535

FRICTIONLESS TRACK AND IDERS HAVING AIR BEARING S FACES FOR DEMONSTRATING ME NICAL PRINCIPLES Filed Nov. L0, 1964 2 Sheets-Sheet 2 4 M F165 INVENTOR ATTORNEYS A; I 56 at ML. S

W r 14. 7/5 7 morm mli'uaqv 01m United States Patent 3,299,535 FRICTIONLESS TRACK AND GLIDERS HAVING AIR BEARING SURFACES F012 DEMGNSTRAT- ING MECHANICAL PRINCIPLES John L. Stull, Alfred, N.Y., and Frank E. Ferguson, Lexington, 'Mass., assignors to The Ealing Corporation, Cambridge, Mass, a corporation of Delaware Filed Nov. 10, 1964, Ser. No. 410,110 8 Claims. (Cl. 35-19) The present invention relates to educational and experimental apparatus and, more particularly, to apparatus by which the principles of mechanics may be represented in terms of a plurality of gliders on a guide, the friction between which is eliminated as a practical matter by 111- brication in the form of compressed air. Such apparatus is useful in connection with demonstration of and experimentation in such physical principles as impact in terms of colliding gliders, acceleration of gravity in terms of a glider on a tilted guide, etc.

The object of the present invention is to provide a novel guide and glider arrangement of the foregoing type, in which the guide and gliders combine unprecedently inexpensive configurations with p-articular-ly efficacious operation. The guide is a hermetic tube of triangular crosssectional shape having a horizontal base portion and a pair of equal side portions. The base portion is provided at intervals with pairs of adjustable supports for precision fastening to a rigid support. The gliders, of which there are a plurality, are characterized by a pair of downwardly diverging leg portions, an upwardly extending shank portion and a transversely extending head portion. The center of gravity of the total mass is positioned above the apex of the leg portions in order that a spring positioned at that point can absorb desired applied force without generating undesired resulting torque. The system as a whole is such that notches in the head portions of the gliders cooperate with a taut line associated with the guide in order to simplify adjustment procedures,

Other objects of the present invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the apparatus possessing the structure, components and arrangement of parts which are exemplified in the following detailed disclosure. For a full understanding of the nature and objects of the present invention, reference is made to the following detailed description, taken in connection with the accompanying drawing, wherein:

' FIG. 1 is a perspective view of a preferred apparatus embodying the present in ention:

FIG. 1A is a detail view of the apparatus of FIG. 1;

FIG. 1B is another view of the apparatus of FIG. 1;

FIG. 2 is a cross-sectional view of theguide of the apparatus of FIG. 1;

FIG. 3' is a cross-sectional view of a glider of the apparatus of FIG. 1;

FIG. 4 is a cross-sectional view of the apparatus of FIG. 1 as provided with an end stop afiixed thereto;

FIG. 5 is a perspective view of the end stop of FIG. 4 in one of its uses; and

FIG. 6 is a perspective view of a portion of a modification of the apparatus of FIG. 1.

Generally, the illustrated apparatus comprises a beam support 10 (shown in FIG. 1 as an I-beam), a track 12 and a plurality of gliders 14. I-beam. 10* provides a rigid and stable base that is sufiiciently elongated to support track 12 in its entirety. Track 12 is closed at its ends except for a port through which air is introduced under pressure from a suitable supply 16. Gliders 14, which are supported on a thin film of air supplied from within track 12 through vents, are provided with a multiplicity of features by which the arrangement as a whole may be adjusted for optimum operation, by which weights and other operating components may be attached and by which indicating elements may be affixed.

As shown, beam 10 includes a base cross-piece 18, a medial upright piece 20 and a platform cross-piece 22, composed of ferrous or extruded aluminum stock. Track 12, in the form of an extruded aluminum tube of triangular cross-section, has a horizontal base portion 23 and a pair of upwardly converging side portions 25, 27. Preferably, the apex angle of the cross-sectional triangle is approximately and the lower acute angles of the crosssectional triangle are each approximately 45. Formed in parallelism along the lower extremity of side portion 25 (FIG. la) of guide 12 is a longitudinally extending slot 26 in which is positioned a graduated steel rule 28 having visible indicia. Formed in parallelism along the lower extremity of side portion 27 is a slot 32, the crosssectional configuration of which is outwardly convex. Flexed within slot 32 is a marking strip 34-, the central portion of which is slightly spaced from the corresponding portion of slot 32 when its longitudinal edges are snugly fitted into the longitudinal edges of slot 32. Although strip 34 may be merely composed of paper or some like ink-receptive material, in the form shown, it is composed of a heat sensitive strip capable of being visibly marked by the application of high voltage sparks in a manner to be described below. At positions adjacent the apex between side portions 25 and 27 and at positions downwardly spaced therefrom are parallel rows of .apertures 36, 38 and 40, 42. These apertures permit the escape of compressed air from within track 12 in order to support gliders 14. At the underside of base portion 23 of track 12 are a series of pairs of coupling mounts 44, each in the form of a depending screw 46, (FIGS. 1 and 2) together with lock nuts and washers that are identical to those shown at in FIG. 6. It will be apparent that by adjustment of the nuts throughout the length of track 12 even very minor geometrical variations due to torsion, bending and other deformations may be adjusted in order to provide a virtually perfect bed, of desired rectilinear or curvilinear shape, for the film of compressed air upon which gliders 14 may move. In this manner the slope .and/ or the shape may be controlled. The provision of depending screws 46 of substantial length (2 to 4 inches) and thin cross-section at one provides both rigid transverse coupling of the track to the beam in terms of torsion and bending correction yet has lesser longitudinal coupling allowing for necessary track elongation due to thermal expansion with minimum effect on predetermined track conformation.

Each of the gliders 14 includes a pair of downwardly diverging leg portions 54, 56, which subtend an apex angle equal to or less than the apex track angle, in the present case 90. Upwardly extending from the apex is a body portion 58 and transversely extending upon the body portion is a balancing mast portion 60. The crosssectional center of mass of glider 14 in the vicinity of 62, which is above the apex angle between leg portions 54, 56. Turned into a tapped bore on the line of the center of mass 62 at one extremity of glider 14 is a screw by which an annular spring 64 is attached. At the opposite extremity of the glider on the line of the center of mass gravity is a corresponding leaf spring arrangement 66. In the upper face of mount portion 60 is a rectangular notch 68 extending completely the length of the balancing mast portion 60. Notch 68 is adapted to receive a sight line 70, to be described in greater detail below, by which the desired positioning and conforming of track 12 via dependent screws 46 may be accomplished.

Indicators are associated with gliders 14 as follows. An insulating rod 72 is fastened to body portion 58 by a suitable screw. Extending perpendicularly from body portion 58 and reversely curved into contiguity with recording strip 34 is a conducting wire 74, which is supported at the outward extremity of rod 72. The most outward extremity of Wire 74 is contiguous with a high voltage track spark wire 85, which is tensioned along track 12 in parallelism therewith. Wire 86 is carried at its ends by insulating mounts 88 affixed to the track stops. Wire 86 is provided with intermittent high voltage to direct electrical pulses through wire and through recording strip 34, to the track which is ground. Extending through body portion 58 equally on opposite sides on line of the center of mass is a mounting support 90 upon which may be positioned suitable weights 92 of different masses. The edge of portion 54. serves as a pointer for association with scale 28.

In operation, first at least one glider 14 is positioned at spaced intervals along track 12. Opposite ends of sight line 70 are attached to end stops 100 at opposite extremities of track 12 (FIGS. 4 and 5). These end stops are shaped like gliders 14 but are bolted to track 12 as by nuts and Washers lltiZ. Each of the end stops is provided with a centering nick 104. Each end of sight line '70 is attached to end stop 1% as at 105 and passes through nick 104 and over a leaf spring 108 to a tensioning turnbuckle llt Next beam iii is leveled transversely by means of spirit levels at various positions therealong. Next track 12 is coarsely adjusted for track shape by viewing line 70 transversely across the top of glider 14 and by adjustment of the pairs of mounts 44 therealong. Fine adjustment is effected by minimizing drift of a glider in position with air pressure on. The air escaping through vents 36, 38, 40, 42, float the gliders which then seek to rest in low spots of the track. Successive fine adjustments of dependent screws and nuts reduce glider motion to minimal levels. Next, with appropriate weights 92 supported on cross-mount 962, chosen glider 14 is positioned at chosen positions along track 12 with the aid of indi-cia 28. Wire 74-, being aligned in proximity with recording strip 34 and high voltage line 86, the glider is then set in motion. A sequence of high voltage pulses is applied through wire 74 to produce intermittent glider position markings on recording strip 34 during the conduction of experiments or investigations of types that will be understood by persons skilled in the art.

An alternative beam configuration is shown in FIG. 6 as box-like in cross-section having a pair of opposed vertical panels 112, 114, a pair of opposed horizontal channels 115, 118 and two pairs of outwardly directed ribs 12%, 122 and 124-, 126. Guide 12 is fixedly mounted on ribs 126, 122 by suitable nut and bolt arrangements 125. The beam configuration, either the I-beam of FIG. 1 or the box-beam of FIG. 6, in turn is supported in practice at its ends on one or more cross-pieces of adjustable height by which the over-all slope of the beam and track is determined.

The illustrated embodiment of the present invention provides a versatile and efiicacio-us apparatus for demonstrating and experimenting under near frictionless conditions in connection with the principles of physical mechanics. Since certain changes may be made in the foregoing disclosure without departing from the scope of the invention herein involved, it is intended that all matter shown in the accompanying drawings and described above be interpreted in an illustrative and not a limiting sense.

What is claimed:

1. A device for experimenting and demonstrating in connection with physical, mechanical principles, said device comprising a track in the form of a hollow tube of triangular cross-section, said tube having a substantially horizontal cross-portion and a pair of downwardly diverging leg portions connected to each other and to said cross-portion said diverging leg portions having vent means for the transmision of air, ends of said tube being closed except for an opening for the introduction of compressed air, a plurality of gliders, each of said gliders having a pair of downwardly diverging leg portions having an apex and a body portion extending upwardly from said apex, the center of gravity of said glider being above said apex, said glider leg portions straddling said leg portions of said track.

2. The device of claim 1 wherein said track is composed of extruded light metal.

3. The device of claim 1 wherein said leg portions and said body portion of said glider are composed of extruded light metal.

4. The device of claim 1 wherein spring means is connected to said glider at said center of gravity.

5. A device for experimenting and demonstrating in connection with physical principles, said device comprising an I-beam including upper and lower horizontal crosspieces and a medial vertical cross-piece connected integrally therebetween, a track in the form of a hollow tube of triangular cross-section, said tube having a substantially horizontal wall portion and a pair of downwardly diverging wall portions connected to each other and to said horizontal wall portion, ends of said tube being closed except for an opening for the introduction of compressed air, the apex angle between said downwardly diverging wall portions being approximately 90, one of said wall portions having in sequence from said apex a first row of apertures, a second row of apertures and a longitudinal groove, a graduated rule in said groove, the other of said downwardly diverging wall portions having in sequence from said apex a first row of apertures, a second row of apertures and a longitudinal groove, said second-mentioned longitudinal groove having an outwardly convex curved surface, a recording strip in said second-mentioned longitudinal groove, the medial portions of said recording strip being slightly spaced from the medial portions of said second-mentioned longitudinal groove, a plurality of pairs of threaded members extending downwardly from said horizontal wall portion of said track, the effective length of said members being adjustable, a plurality of gliders, each of said gliders having a pair of downwardly diverging leg portions having an apex, a body portion extending upwardly from said second-mentioned apex and a cross-portion medially mounted on said body portion, the center of mass of said glider being above said second-mentioned apex, said leg portions straddling said downwardly depending diverging wall portions of said track, a spring mounted in association with said center of mass, pointer means on one of said leg portions for association with said graduated scale, and an insulating means on said glider, a probe extending from said insulating means, said probe being in registration both with said recording strip and an electrically conducting rail mounted on said track, said probe being operatively connected to said electrically conducting rail, a slot in said cross-portion extending along said track, and a plurality of removable weights for selective attachment to said gliders.

6. The device of claim 5 wherein said I-beam, said track and said gliders are composed of extruded light metal.

7. A device for experimenting and demonstrating in connection with physical principles, said device comprising a box-beam including upper and lower horizontal cross-pieces and a medial tube connected integrally therebetween, a track in the form of a hollow tube of triangular cross-section, said tube having a substantially horizotnal wall portion and a pair of downwardly diverging wall portions connected to each other and to said horizontal wall portion, ends of said tube being closed except for an opening for the introduction of compressed air, the apex angle between said downwardly diverging wall portions being approximately 90, one of said wall portions having in sequence from said apex a first row of apertures, a second row of apertures and a longitudinal groove, a graduated rule in said groove, the other of said downwardly diverging wall portions having in sequence from said apex a first row of apertures, a second row of apertures and a longitudinal groove, said second-mentioned longitudinal groove having an outwardly convex curved surface, a recording strip in said secondmentioned longitudinal groove, the medial portion of said recording strip being slightly spaced from the medial portions of said second-mentioned longitudinal groove, a plurality of pairs of threaded members extending downwardly from said horizontal wall portion of said track, the eifective length of said members being adjustable, a plurality of gliders, each of said gliders having a pair of downwardly diverging leg portions having an apex, a body portion extending upwardly from said secondmentioned apex and a cross-portion medially mounted on said body portion, the center of mass of said glider being above said second-mentioned apex, said leg portions straddling said downwardly depending diverging wall portions of said track, a spring mounted in association with said center of mass, pointer means on one of said leg portions for association with said graduated scale, and an insulating means on said glider, a probe extending from said insulating means, said probe being in registration with both said recording strip, and an electrically conducting rail mounted on said track, said probe being operatively connected to said electrically conducting rail, a slot in said cross-portion extending along said track, and a plurality of removable weights for selective attachment to said gliders.

8. The device of claim 7 wherein said box-beam, said track and said gliders are composed of extruded light metal.

References Cited by the Examiner UNITED STATES PATENTS 2,805,898 9/1957 Willis 302-29 EUGENE R. CAPOZIO, Primary Examiner.

H. S. SKOGQUIST, Assistant Examiner. 

1. A DEVICE FOR EXPERIMENTING AND DEMONSTRATING IN CONNECTION WITH PHYSICAL, MECHANICAL PRINCIPLES, SAID DEVICE COMPRISING A TRACK IN THE FORM OF A HOLLOW TUBE OF TRIANGULAR CROSS-SECTION, SAID TUBE HAVING A SUBSTANTIALLY HORIZONTAL CROSS-PORTION AND A PAIR OF DOWNWARDLY DIVERGING LEG PORTIONS CONNECTED TO EACH OTHER AND TO SAID CROSS-PORTION SAID DIVERGING LEG PORTIONS HAVING VENT MEANS FOR THE TRANSMISSION OF AIR, ENDS OF SAID TUBE BEING CLOSED EXCEPT FOR AN OPENING FOR THE INTRODUCTION OF COMPRESSED AIR, A PLURALITY OF GLIDERS, EACH OF SAID GLIDERS HAVING A PAIR OF DOWNWARDLY DIVERGING LEG PORTIONS HAVING AN APEX AND A BODY PORTION EXTENDING UPWARDLY FROM SAID APEX, THE CENTER OF GRAVITY OF SAID GLIDER BEING ABOVE SAID APEX, SAID GLIDER LEG PORTIONS STRADDLING SAID LEG PORTIONS OF SAID TRACK. 